Multi-fiber optical connectors are widely used by telecommunication system operators for various applications. Multi-fiber connectors are predominantly MPO fiber connectors. Commercially available MPO fiber connectors include fiber counts of, for example, 8, 12, 24, 48, or 72 fibers. For single mode (SM) fiber connectors which has much smaller fiber alignment tolerance than multimode fibers due to its much smaller fiber core, the most common fiber count of SM MPO connectors is 12 fibers today. Higher fiber count SM MPO connectors such as 24 or 48 fibers are also possible, although their optical performance deteriorates seriously compared to 12 fiber SM MPO connectors.
In part, the deteriorating performance with higher fiber counts is because conventional connectors are made with traditional polymer molding techniques; these molding techniques cannot achieve the precise alignment required. For example, physical pins must be positioned accurately in the mold to form the fiber holes and guide holes. However, it is very difficult to use molding to achieve a higher count 2-dimensional (2D) fiber holes accurately.
To satisfy the increasing demand of massive data transfer, components in optical communication systems are being developed to be miniaturized and highly integrated. Particularly, integrating large numbers of SM fibers (such as 144 or 576) on a single fiber connector is a long-felt need. However, great challenges lie in the fabrication of such fiber connectors.
There have been several approaches to make multi-fiber connectors with high- density 2D fiber arrays. In the following, each approach is reviewed.
1) Traditional MPO Multi-Fiber Connector
MPO connectors use MT connector ferrules to align the fibers. The MT connector ferrules for SM fibers typically have one linear array of 12 or 8 fiber holes, and two large guide holes for guide pin alignment.
MT connector ferrules are plastic parts made by plastic molding processes. Because fiber holes and guide holes are formed by molding plastics around physical pins in the mold, when there is a high count 2D array of physical pins, it is very difficult to position these pins accurately and replicate the mold faithfully.
Although a 72-fiber multimode MPO connector in a 2D configuration (12×6) has been introduced by some manufacturers, its geometrical precision of fiber holes and guide holes is far inferior to 12-fiber multimode MPO connectors. In addition, a SM fiber version of this connector is unavailable.
The operating principle of traditional MPO connectors is physical contact. Fibers are polished so that they protrude from the surrounding MT ferrule surface, to ensure uniform physical contact of every fiber surface. Higher fiber count MPO connectors not only have problems with SM fiber alignment tolerance, they also suffer from problems such as poor physical contact and sensitivity to dust and contaminants.
2) MXC Connector
In 2013, MXC connectors with 64 fibers using lenses were announced by Corning, Intel, and US Conec. While the lens-based design allows this connector to operate without physical contact and ensure much more robust connection, insertion loss is high (0.8 dB insertion loss) even for multimode fiber. Furthermore, MXC connectors are not availability for SM fiber.
The fiber ferrules in the MXC connectors are made by molding plastics, so these connectors suffer the same limitations as MPO connector ferrules.
A previous approach to non-contact fiber connectors is described by the inventor of the present application in U.S. patent application Ser. No. 13/725,087, filed Dec. 21, 2012, the disclosure of which is incorporated by reference herein.
Thus, there is a need in the art for improved manufacturing techniques for forming high-precision multi-fiber optical fiber connectors, especially for SM fibers. Such high precision multi-fiber optical fiber connectors could be used to terminate the large number of optical fibers needed in modern data centers and telecommunication systems.